The blood-brain barrier and the meningeal blood-cerebrospinal fluid barrier (mBCSFB) are formed by brain endothelial cells (BECs), protecting the brain from harmful substances. BECs express efflux transporters, P-glycoprotein (P-gp), and breast cancer resistance protein (BCRP), which actively pump endogenous and exogenous substances from the brain to the blood. Despite the crucial role of efflux transporters in the brain, there is still a considerable gap in our understanding of their activity in response to environmental factors such as pathogens.

Neisseria meningitidis (Nm), a commensal bacterium of the respiratory tract, can cause meningitis through systemic spread and transmigration across mBCSFB. Little is known about the impact of Nm on efflux transporters in the brain. This study aims to decipher the impact of Nm on P-gp and BCRP activity in BECs.

iPSCs were differentiated into BECs as previously described (Stebbins et al., 2016). The impact of Nm on P-gp and BCRP was analyzed by RT-qPCR and immunoblotting. P-gp and BCRP activity was assessed by measuring intracellular accumulation of Rhodamine 123 (R123) and Chlorin e6 (Ce6), respectively.

The uptake of R123 and Ce6 by P-gp and BCRP under exposure to their inhibitors, PSC833 and Ko143, respectively confirmed their activity in iBECs. Following Nm infection, a notable decrease in P-gp activity was observed despite changes in expression and protein level. In contrast to P-gp, BCRP activity remained unaffected. Our data suggested an essential role for the Nm capsule in P-gp dysfunction since non-capsulated Nm did not impact the R123 accumulation. Moreover, we observed that live Nm is required for P-gp inhibition.

The decline in P-gp activity during Nm infection suggests a dynamic response to Nm at the level of activity. Consistent with earlier research, unaltered BCRP activity suggests a potential compensatory relationship with P-gp (Lye et al., 2023). Our data identified a crucial role for the Nm capsule in P-gp inhibition, presenting a potential therapeutic target for drug delivery. Our observation emphasizes the requirement of live Nm for P-gp inhibition, highlighting the host-pathogen interaction.